[DOCS-7981] Add Datadog Agent source to log volume control

[maycmlee]

What does this PR do? What is the motivation?

Adds the Datadog Agent source page for the Log Volume Control use case. The doc uses mostly existing general reuse shortcodes so there isn't a lot of new content to review.

DOCS-7981

Merge instructions

• Please merge after reviewing

Additional notes

[github-actions]

Preview links (active after the build_preview check completes)

New or renamed files

• https://docs-staging.datadoghq.com/may/add-dd-agent-to-lvc/observability_pipelines/log_volume_control/datadog_agent

Modified Files

• https://docs-staging.datadoghq.com/may/add-dd-agent-to-lvc/observability_pipelines/log_volume_control/
• https://docs-staging.datadoghq.com/may/add-dd-agent-to-lvc/observability_pipelines/log_volume_control/splunk_hec
• https://docs-staging.datadoghq.com/may/add-dd-agent-to-lvc/observability_pipelines/log_volume_control/splunk_tcp
• https://docs-staging.datadoghq.com/may/add-dd-agent-to-lvc/observability_pipelines/log_volume_control/sumo_logic_hosted_collector

[brett0000FF]

Looks nice! I like how you laid this out. All of the shortcodes made this easy to review. I checked the preview to make sure nothing funky was happening too.

[p-parekh]

May, I am wondering if we should move the "Connect your DD agent to OP" section ahead of setting up the destinations? Currently we talk about setting up source->dest->source. I am proposing setting up source completely before moving to destination. Thoughts?

[maycmlee]

May, I am wondering if we should move the "Connect your DD agent to OP" section ahead of setting up the destinations? Currently we talk about setting up source->dest->source. I am proposing setting up source completely before moving to destination. Thoughts?

@p-parekh I'm pretty sure I brought this up when we were getting the OP 2.0 docs ready for the launch and Barry and Eugene said it makes more sense for that section to be at the end because users are going through the UI to build the pipeline first. After the pipeline is ready, then they should start sending logs to it.